Selection signatures in Canchim beef cattle.

Selection signature (SS) was assessed in this study by means of the integrated haplotype score (iHS) method, which determines the decay of homozygosity in the surroundings of a core single nucleotide polymorphism (SNP) marker. Canchim breed animals were genotyped using the Illumina BovineHD BeadChip; which has almost 800 thousand SNP markers. Genotype quality control (QC) was applied to exclude SNP with genotype calling score lower than 0.20; SNP with minor allele frequency lower than 0.01; and call rate for SNP and samples which were lower than 0.95 and 0.90, respectively. Only autosomal SNPs with known genome position were used. After the QC, 687,655 SNPs and 396 samples remained for SS analysis. Signals of SS were detected on chromosomes 5, 6, 8, and 14, indicating that these regions are conserved through recent generations

Associations between feed efficiency and aspects of lactation curves in primiparous Holstein dairy cattle.

Genetic selection for improved feed efficiency in dairy cattle has received renewed attention over the last decade to address the needs of a growing global population. As milk yield is a critical component of feed efficiency metrics in dairy animals, our objective was to evaluate the associations between feed efficiency in primiparous Holstein cattle and parameters of a mathematical model describing individual lactation curves. The Dijkstra lactation curve model was fit to individual lactation records from 34 Holstein heifers with previously estimated measures of feed efficiency. We found that the optimal fit of the Dijkstra model was achieved using daily milk yield records up to 21 d in milk to capture the rise to peak milk yield and using monthly dairy herd improvement records for the remainder of lactation to accurately characterize lactation persistency. In the period of lactation before peak milk yield, improved feed efficiency was associated with a faster increase in daily milk yield over a shorter period of time at the expense of increased mobilization of body reserves; this serves to reinforce the concept that dairy cattle are primarily capital breeders versus income breeders. Feed efficiency in the period following peak lactation, as measured by gross feed efficiency, return over feed costs, and net energy efficiency of lactation, was positively associated with higher peak milk yield. The findings in early lactation suggest that estimates of feed efficiency could be improved by evaluating feed efficiency relative to conception, rather than parturition and lactation, to better account for the energy stored and released from body reserves in capital breeding

Selection signatures in Canchim beef cattle.

Selection signature (SS) was assessed in this study by means of the integrated haplotype score (iHS) method, which determines the decay of homozygosity in the surroundings of a core single nucleotide polymorphism (SNP) marker. Canchim breed animals were genotyped using the Illumina BovineHD BeadChip; which has almost 800 thousand SNP markers. Genotype quality control (QC) was applied to exclude SNP with genotype calling score lower than 0.20; SNP with minor allele frequency lower than 0.01; and call rate for SNP and samples which were lower than 0.95 and 0.90, respectively. Only autosomal SNPs with known genome position were used. After the QC, 687,655 SNPs and 396 samples remained for SS analysis. Signals of SS were detected on chromosomes 5, 6, 8, and 14, indicating that these regions are conserved through recent generations

Copy number variation in dairy cattle using next-generation sequencing.

Gene copy number variants (CNV) have been shown to be associated with several production traits in dairy cattle; however, the detection and validation of CNVs in crossbred cattle is currently lacking. In order to provide a basis for future association studies, we sought to identify CNV regions (CNVRs) within the Girolando composite breed resulting from a mating of the Holstein (taurine) and Gir (indicine) breeds. A read depth method was performed using CNVnator software on NGS data from two Girolando, two Gir and ten Holstein bulls. The individual CNVs were merged into CNVRs based on genomic regions overlapping by at least 1 bp. In total, we identified a composite of 1,286 CNVRs (520 deletions, 255 duplications, 511 mixed) on the genomes of all samples. We observed 34 CNVRs (nine deletions, 25 mixed) in common (overlapping > 50%) only between Girolando and Holstein and 181 CNVRs (20 deletions, 21 duplications,140 mixed) only in Girolando and Gir, suggesting parent-of-origin inheritance from Holstein and Gir cattle, respectively. One of these Holstein-specific CNVRs intersected with the interleukin 6 family cytokine (LIF) gene which is linked to fat production and fertility traits in Holstein. Genes related to disease resistance (e.g. the CD4 gene) also coincided with CNVRs present only in Gir and Girolando cattle suggesting an indicine origin for the CNV. These results showed evidence of specific CNVRs shared by Girolando and purebred breeds which may be targeted for future selective breeding.PAG 2018. P0490. Na publicação: Adhemar Zerlotini, Marcos Vinicius B. da Silva

Selection signatures in Canchim beef cattle.

Background: Recent technological advances in genomics have allowed the genotyping of cattle through single nucleotide polymorphism (SNP) panels. High-density SNP panels possess greater genome coverage and are useful for the identification of conserved regions of the genome due to selection, known as selection signatures (SS). The SS are detectable by different methods, such as the extended haplotype homozygosity (EHH); and the integrated haplotype score (iHS), which is derived from the EHH. The aim of this study was to identify SS regions in Canchim cattle (composite breed), genotyped with high-density SNP panel. Results: A total of 687,655 SNP markers and 396 samples remained for SS analysis after the genotype quality control. The iHS statistic for each marker was transformed into piHS for better interpretation of the results. Chromosomes BTA5 and BTA14 showed piHS>5, with 39 and nine statistically significant SNPs (P<0.00001), respectively. For the candidate selection regions, iHS values were computed across the genome and averaged within non-overlapping windows of 500 Kb. We have identified genes that play an important role in metabolism, melanin biosynthesis (pigmentation), and embryonic and bone development. Conclusions: The observation of SS indicates that the selection processes performed in Canchim, as well as in the founder breeds (i.e. Charolais), are maintaining specific genomic regions, particularly on BTA5 and BTA14. These selection signatures regions could be associated with Canchim characterization.Na publicação: Luciana Correia de Almeida Regitano

Selection signatures in Canchim beef cattle.

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